Linux Virtualization - Apr 2007 - [PATCH] Simplify smp_call_function*() by using common implementation

smp_call_function and smp_call_function_single are almost complete
duplicates of the same logic.  This patch combines them by
implementing them in terms of the more general
smp_call_function_mask().

[ Jan, Andi: This only changes arch/i386; can x86_64 be changed in the
  same way? ]

[ Rebased onto Jan's x86_64-mm-consolidate-smp_send_stop patch ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Stephane Eranian <eranian@hpl.hp.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Andi Kleen <ak@suse.de>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Cc: Ingo Molnar <mingo@elte.hu>

---
 arch/i386/kernel/smp.c |  177 +++++++++++++++++++++++-------------------------
 1 file changed, 86 insertions(+), 91 deletions(-)

==================================================================---
a/arch/i386/kernel/smp.c
+++ b/arch/i386/kernel/smp.c
@@ -515,14 +515,26 @@ void unlock_ipi_call_lock(void)
 
 static struct call_data_struct *call_data;
 
-static void __smp_call_function(void (*func) (void *info), void *info,
-				int nonatomic, int wait)
+
+static int __smp_call_function_mask(cpumask_t mask,
+				    void (*func)(void *), void *info,
+				    int wait)
 {
 	struct call_data_struct data;
-	int cpus = num_online_cpus() - 1;
+	cpumask_t allbutself;
+	int cpus;
+
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
+	allbutself = cpu_online_map;
+	cpu_clear(smp_processor_id(), allbutself);
+
+	cpus_and(mask, mask, allbutself);
+	cpus = cpus_weight(mask);
 
 	if (!cpus)
-		return;
+		return 0;
 
 	data.func = func;
 	data.info = info;
@@ -533,9 +545,12 @@ static void __smp_call_function(void (*f
 
 	call_data = &data;
 	mb();
-	
-	/* Send a message to all other CPUs and wait for them to respond */
-	send_IPI_allbutself(CALL_FUNCTION_VECTOR);
+
+	/* Send a message to other CPUs */
+	if (cpus_equal(mask, allbutself))
+		send_IPI_allbutself(CALL_FUNCTION_VECTOR);
+	else
+		send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 
 	/* Wait for response */
 	while (atomic_read(&data.started) != cpus)
@@ -544,6 +559,34 @@ static void __smp_call_function(void (*f
 	if (wait)
 		while (atomic_read(&data.finished) != cpus)
 			cpu_relax();
+
+	return 0;
+}
+
+/**
+ * smp_call_function_mask(): Run a function on a set of other CPUs.
+ * @mask: The set of cpus to run on.  Must not include the current cpu.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed on other
CPUs.
+ *
+ * Returns 0 on success, else a negative status code. Does not return until
+ * remote CPUs are nearly ready to execute <<func>> or are or have
finished.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int smp_call_function_mask(cpumask_t mask,
+			     void (*func)(void *), void *info,
+			     int wait)
+{
+	int ret;
+
+	spin_lock(&call_lock);
+	ret = __smp_call_function_mask(mask, func, info, wait);
+	spin_unlock(&call_lock);
+
+	return ret;
 }
 
 /**
@@ -559,20 +602,43 @@ static void __smp_call_function(void (*f
  * You must not call this function with disabled interrupts or from a
  * hardware interrupt handler or from a bottom half handler.
  */
-int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
-			int wait)
-{
-	/* Can deadlock when called with interrupts disabled */
-	WARN_ON(irqs_disabled());
-
-	/* Holding any lock stops cpus from going down. */
-	spin_lock(&call_lock);
-	__smp_call_function(func, info, nonatomic, wait);
-	spin_unlock(&call_lock);
-
-	return 0;
+int smp_call_function(void (*func) (void *info), void *info, int nonatomic,
+		      int wait)
+{
+	return smp_call_function_mask(cpu_online_map, func, info, wait);
 }
 EXPORT_SYMBOL(smp_call_function);
+
+/*
+ * smp_call_function_single - Run a function on another CPU
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @nonatomic: Currently unused.
+ * @wait: If true, wait until function has completed on other CPUs.
+ *
+ * Retrurns 0 on success, else a negative status code.
+ *
+ * Does not return until the remote CPU is nearly ready to execute <func>
+ * or is or has executed.
+ */
+int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
+			     int nonatomic, int wait)
+{
+	/* prevent preemption and reschedule on another processor */
+	int ret;
+	int me = get_cpu();
+	if (cpu == me) {
+		WARN_ON(1);
+		put_cpu();
+		return -EBUSY;
+	}
+
+	ret = smp_call_function_mask(cpumask_of_cpu(cpu), func, info, wait);
+
+	put_cpu();
+	return ret;
+}
+EXPORT_SYMBOL(smp_call_function_single);
 
 static void stop_this_cpu (void * dummy)
 {
@@ -598,7 +664,7 @@ void smp_send_stop(void)
 	unsigned long flags;
 
 	local_irq_save(flags);
-	__smp_call_function(stop_this_cpu, NULL, 0, 0);
+	__smp_call_function_mask(cpu_online_map, stop_this_cpu, NULL, 0);
 	if (!nolock)
 		spin_unlock(&call_lock);
 	disable_local_APIC();
@@ -641,77 +707,6 @@ fastcall void smp_call_function_interrup
 	}
 }
 
-/*
- * this function sends a 'generic call function' IPI to one other CPU
- * in the system.
- *
- * cpu is a standard Linux logical CPU number.
- */
-static void
-__smp_call_function_single(int cpu, void (*func) (void *info), void *info,
-				int nonatomic, int wait)
-{
-	struct call_data_struct data;
-	int cpus = 1;
-
-	data.func = func;
-	data.info = info;
-	atomic_set(&data.started, 0);
-	data.wait = wait;
-	if (wait)
-		atomic_set(&data.finished, 0);
-
-	call_data = &data;
-	wmb();
-	/* Send a message to all other CPUs and wait for them to respond */
-	send_IPI_mask(cpumask_of_cpu(cpu), CALL_FUNCTION_VECTOR);
-
-	/* Wait for response */
-	while (atomic_read(&data.started) != cpus)
-		cpu_relax();
-
-	if (!wait)
-		return;
-
-	while (atomic_read(&data.finished) != cpus)
-		cpu_relax();
-}
-
-/*
- * smp_call_function_single - Run a function on another CPU
- * @func: The function to run. This must be fast and non-blocking.
- * @info: An arbitrary pointer to pass to the function.
- * @nonatomic: Currently unused.
- * @wait: If true, wait until function has completed on other CPUs.
- *
- * Retrurns 0 on success, else a negative status code.
- *
- * Does not return until the remote CPU is nearly ready to execute <func>
- * or is or has executed.
- */
-
-int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
-			int nonatomic, int wait)
-{
-	/* prevent preemption and reschedule on another processor */
-	int me = get_cpu();
-	if (cpu == me) {
-		WARN_ON(1);
-		put_cpu();
-		return -EBUSY;
-	}
-
-	/* Can deadlock when called with interrupts disabled */
-	WARN_ON(irqs_disabled());
-
-	spin_lock_bh(&call_lock);
-	__smp_call_function_single(cpu, func, info, nonatomic, wait);
-	spin_unlock_bh(&call_lock);
-	put_cpu();
-	return 0;
-}
-EXPORT_SYMBOL(smp_call_function_single);
-
 static int convert_apicid_to_cpu(int apic_id)
 {
 	int i;

On Tue, 27 Mar 2007 15:13:29 -0700 Jeremy Fitzhardinge wrote:
> smp_call_function and smp_call_function_single are almost complete
> duplicates of the same logic.  This patch combines them by
> implementing them in terms of the more general
> smp_call_function_mask().
> 
> [ Jan, Andi: This only changes arch/i386; can x86_64 be changed in the
>   same way? ]
> 
> [ Rebased onto Jan's x86_64-mm-consolidate-smp_send_stop patch ]
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
> Cc: Jan Beulich <jbeulich@novell.com>
> Cc: Stephane Eranian <eranian@hpl.hp.com>
> Cc: Andrew Morton <akpm@osdl.org>
> Cc: Andi Kleen <ak@suse.de>
> Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
> Cc: Ingo Molnar <mingo@elte.hu>
> 
> ---
>  arch/i386/kernel/smp.c |  177
+++++++++++++++++++++++-------------------------
>  1 file changed, 86 insertions(+), 91 deletions(-)
> 
> ==================================================================> ---
a/arch/i386/kernel/smp.c
> +++ b/arch/i386/kernel/smp.c
> @@ -544,6 +559,34 @@ static void __smp_call_function(void (*f
>  	if (wait)
>  		while (atomic_read(&data.finished) != cpus)
>  			cpu_relax();
> +
> +	return 0;
> +}
> +
> +/**
> + * smp_call_function_mask(): Run a function on a set of other CPUs.
> + * @mask: The set of cpus to run on.  Must not include the current cpu.
> + * @func: The function to run. This must be fast and non-blocking.
> + * @info: An arbitrary pointer to pass to the function.
> + * @wait: If true, wait (atomically) until function has completed on other
CPUs.
> + *
> + * Returns 0 on success, else a negative status code. Does not return
until
> + * remote CPUs are nearly ready to execute <<func>> or are or
have finished.
                                              func() or <what>??
      and what does "nearly ready" mean?
> + *
> + * You must not call this function with disabled interrupts or from a
> + * hardware interrupt handler or from a bottom half handler.
> + */
> +int smp_call_function_mask(cpumask_t mask,
> +			     void (*func)(void *), void *info,
> +			     int wait)
> +{
> +	int ret;
> +
> +	spin_lock(&call_lock);
> +	ret = __smp_call_function_mask(mask, func, info, wait);
> +	spin_unlock(&call_lock);
> +
> +	return ret;
>  }
>  
>  /**
> @@ -559,20 +602,43 @@ static void __smp_call_function(void (*f
>   * You must not call this function with disabled interrupts or from a
>   * hardware interrupt handler or from a bottom half handler.
>   */
> -int smp_call_function (void (*func) (void *info), void *info, int
nonatomic,
> -			int wait)
> -{
> -	/* Can deadlock when called with interrupts disabled */
> -	WARN_ON(irqs_disabled());
> -
> -	/* Holding any lock stops cpus from going down. */
> -	spin_lock(&call_lock);
> -	__smp_call_function(func, info, nonatomic, wait);
> -	spin_unlock(&call_lock);
> -
> -	return 0;
> +int smp_call_function(void (*func) (void *info), void *info, int
nonatomic,
> +		      int wait)
> +{
> +	return smp_call_function_mask(cpu_online_map, func, info, wait);
>  }
>  EXPORT_SYMBOL(smp_call_function);
> +
> +/*
   /**
> + * smp_call_function_single - Run a function on another CPU
> + * @func: The function to run. This must be fast and non-blocking.
> + * @info: An arbitrary pointer to pass to the function.
> + * @nonatomic: Currently unused.
> + * @wait: If true, wait until function has completed on other CPUs.
> + *
> + * Retrurns 0 on success, else a negative status code.
      Returns
> + *
> + * Does not return until the remote CPU is nearly ready to execute
<func>
Same comments:  what is "nearly ready"?  and s/<func>/func()/
> + * or is or has executed.
      Huh?  or what??
> + */
> +int smp_call_function_single(int cpu, void (*func) (void *info), void
*info,
> +			     int nonatomic, int wait)
> +{
> +	/* prevent preemption and reschedule on another processor */
> +	int ret;
> +	int me = get_cpu();
> +	if (cpu == me) {
> +		WARN_ON(1);
> +		put_cpu();
> +		return -EBUSY;
> +	}
> +
> +	ret = smp_call_function_mask(cpumask_of_cpu(cpu), func, info, wait);
> +
> +	put_cpu();
> +	return ret;
> +}
> +EXPORT_SYMBOL(smp_call_function_single);
>  
>  static void stop_this_cpu (void * dummy)
>  {
> @@ -641,77 +707,6 @@ fastcall void smp_call_function_interrup
>  	}
>  }
>  
> -/*
> - * this function sends a 'generic call function' IPI to one other
CPU
> - * in the system.
> - *
> - * cpu is a standard Linux logical CPU number.
> - */
> -static void
> -__smp_call_function_single(int cpu, void (*func) (void *info), void *info,
> -				int nonatomic, int wait)
> -{
> -	struct call_data_struct data;
> -	int cpus = 1;
> -
> -	data.func = func;
> -	data.info = info;
> -	atomic_set(&data.started, 0);
> -	data.wait = wait;
> -	if (wait)
> -		atomic_set(&data.finished, 0);
> -
> -	call_data = &data;
> -	wmb();
> -	/* Send a message to all other CPUs and wait for them to respond */
> -	send_IPI_mask(cpumask_of_cpu(cpu), CALL_FUNCTION_VECTOR);
> -
> -	/* Wait for response */
> -	while (atomic_read(&data.started) != cpus)
> -		cpu_relax();
> -
> -	if (!wait)
> -		return;
> -
> -	while (atomic_read(&data.finished) != cpus)
> -		cpu_relax();
> -}
> -
> -/*
> - * smp_call_function_single - Run a function on another CPU
> - * @func: The function to run. This must be fast and non-blocking.
> - * @info: An arbitrary pointer to pass to the function.
> - * @nonatomic: Currently unused.
> - * @wait: If true, wait until function has completed on other CPUs.
> - *
> - * Retrurns 0 on success, else a negative status code.
> - *
> - * Does not return until the remote CPU is nearly ready to execute
<func>
> - * or is or has executed.
> - */
> -
> -int smp_call_function_single(int cpu, void (*func) (void *info), void
*info,
> -			int nonatomic, int wait)
> -{
> -	/* prevent preemption and reschedule on another processor */
> -	int me = get_cpu();
> -	if (cpu == me) {
> -		WARN_ON(1);
> -		put_cpu();
> -		return -EBUSY;
> -	}
> -
> -	/* Can deadlock when called with interrupts disabled */
> -	WARN_ON(irqs_disabled());
> -
> -	spin_lock_bh(&call_lock);
> -	__smp_call_function_single(cpu, func, info, nonatomic, wait);
> -	spin_unlock_bh(&call_lock);
> -	put_cpu();
> -	return 0;
> -}
> -EXPORT_SYMBOL(smp_call_function_single);
> -
>  static int convert_apicid_to_cpu(int apic_id)
>  {
>  	int i;

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

On Wednesday 28 March 2007 00:13, Jeremy Fitzhardinge
wrote:
> smp_call_function and smp_call_function_single are almost complete
> duplicates of the same logic.  This patch combines them by
> implementing them in terms of the more general
> smp_call_function_mask().
I think I got those already.

-Andi